#define _CRT_SECURE_NO_WARNINGS 1
class Solution {
public:
    char firstNotRepeatingChar(string s) {
        int a[256];
        memset(a, 0, sizeof(a));
        for (int i = 0; i < s.size(); i++)
            a[s[i]]++;
        for (int i = 0; i < s.size(); i++)
            if (a[s[i]] == 1)
                return s[i];
        return '#';
    }
};